Session X - Pelvis/Geriatrics

*Outcome of Total Hip Replacement after Previous Acetabular Fracture vs. Total Hip Replacement for Arthritis: A Matched Cohort Study

Cornelia M. Borkhoff, MSc; Gautam Zaveri, MD; Hans J. Kreder, MD; Matthew J. Jimenez, MD; James P. Waddell, MD; David J.G. Stephen, MD; Marvin Tile, MD, Sunnybrook & Women's College Health Science Center and St. Michael's Hospital, Toronto, ON, Canada (all authors ­ a-Canadian Orthopaedic Foundation Grant; AO-ASIF Foundation Grant)

Purpose: High early failure rates have been documented for total hip replacement (THR) after previous repair of acetabular fractures. Validated functional outcome has not previously been reported. We compared patient outcome after THR for previous acetabular fracture with replacement for idiopathic osteoarthritis.

Methods: A total of 92 patients (60 men and 32 women) with 94 previous acetabular fractures that later required THR were matched by gender, age, and year of THR to patients who received THR for idiopathic osteoarthritis. All patients were included, irrespective of whether or not they had undergone subsequent revision, in order to obtain a true comparison between the two cohorts. Function was measured with use of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Musculoskeletal Function Assessment (MFA). Details regarding the injury, fracture management, the THR and complications were gathered from the hospital chart. A single observer, blinded to patient outcome, reviewed the follow-up radiographs.

Results: A total of 92 patients were in each of the two matched groups (64% men, mean age of 53 ± 13 years). The mean length of follow-up was 7.4 years (range, 2 to 24). Of the 94 acetabular fractures, 65 were treated by ORIF. The average time from fracture to primary THR was 8.2 years (range, 2 days to 47 years). Patients with a previous acetabular fracture had lower WOMAC scores (mean difference, 13.1, 95% CI , 5, 21) than arthritis patients, representing more pain and stiffness and worse function. Overall MFA scores were also significantly worse in the fracture group (mean difference,15.8, 95% CI, 9, 23). For patients with a previous acetabular fracture, the mean overall MFA score was 30.1 ± 17.3, compared with 14.3 ± 11.2 for arthritis patients (the normative mean MFA overall score is 9.3). Lower extremity function, sleep, and activities of daily living were particularly adversely affected. The primary reason that patients with a previous fracture required a THR was severe osteoarthritis; 66% of the patients had radiographic evidence of osteoarthritis. Extensive avascular necrosis in the fracture patients was another reason for a THR. In addition, 17% of patients in the fracture group had evidence of heterotopic ossification, compared with none in the arthritis group (P <0.001). There were three infections in the fracture group and none in the arthritis group. There was no difference in the rate of dislocation, loosening or revision; however, the time to revision was found to be significantly shorter for the fracture group compared with the arthritis group (3.5 ± 4.4 years compared with 7.8 ± 3.9 years, P <0.05). There were 16 patients with a previous acetabular fracture requiring a revision compared with 13 in the elective group. Eight of the 16 patients in the fracture group underwent hip revision within the first year after THR, compared with only 1 in the elective group.

Conclusion: THR after previous acetabular fracture was associated with worse patient function, at a mean follow-up of 7.4 years, than THR for osteoarthritis. Although loosening and revision rates were similar after THR in the two groups, revision total hip replacements occurred earlier among patients with a previous acetabular fracture.